The present invention relates to a temperature sensor having a semiconductor body.
Sensors generally are designed to pick up events in a predominantly technical, although usually not electrical environment and to convert them into electrical signals. The idea of measuring temperature by determining the change in the conductivity of a solid body with temperature variation is connected with the origin of modern physics. This absolute measuring method has the advantage over the relative measurement of temperature by means of the Seebeck effect in that no reference temperature is necessary as, for example, with thermocouples. Temperature sensors which consist of a metallic resistor of nickel or platinum, for instance, are known and are characterized by high stability but also by relatively high manufacturing costs. The desire for an inexpensive temperature sensor led to the utilization of the advantages of silicon planar technology. However, sensors with a pn-junction are difficult to produce because of their space charge zone and the cutoff current, which are a function of temperature.
A temperature sensor is known from German O.S. 2944015 which is based on the principle of the spreading resistance and contains a semiconductor body of silicon, one flat side of which is provided with a layer of silicon dioxide. A metal contact makes connection via a highly doped zone with the semiconductor body through at least one window of the silicon dioxide layer. On the opposite flat side, the semiconductor body is provided with a metal carrier which forms, together with the metal contact, the two leads for the temperature sensor. The spreading-resistance temperature sensor contains no pn-junction. In the single silicon crystal, all the impurity atoms are ionized at normal temperature. An increase of the temperature is therefore not connected with an increase of the number of charge carriers and due to the reduction of the charge carrier mobility by phonon scattering, the conductivity decreases. This temperature sensor therefore has a positive temperature coefficient. The resistance as a function of the temperature is slightly exponential and can be linearized over a wide range, if desired, by connecting an ohmic resistance in parallel.
It is accordingly an object of the invention to improve upon the known temperature sensors of this type. In particular, it is an object of the present invention to provide a temperature sensor having an increased temperature range and a simplified design.